"Versus" Co-op Mode
Coop mode is alright, but it generally makes most brutal outposts incredibly easy and it didn't really hook me.
For the more competitive friends, give us a versus mode where we can both matchmake into the same outpost and try to both complete it as fast as possible. I tried this with some social raids and it was a lot of fun and even made some normal difficulty outposts into a challenge since we were racing eachother and being less careful.
I would absolutely play this kind of thing a lot more than the current coop mode. And it could scale up pretty easily (design-wise) instead of being limited to only 2 players.